The present invention relates to the calibration of a neutral position for hand or foot manual controls such as would be used in a work vehicle, such as, for example a mini excavator or skid steer loader. In particular, the present invention relates to an apparatus and method automatically correcting sensor output drift utilizing a xe2x80x9cmoving averagexe2x80x9d to correct for control and position sensor drift.
Skid steer loaders are work vehicles that include four wheels rotatably mounted to a frame, an engine mounted on the frame and connected by a transmission to rotate at least two wheels, a cab compartment mounted on the frame that includes a seat for an operator, manual controls and a display panel disposed in the cab compartment, a boom arm assembly rotatably mounted on the frame and connected to a pair of hydraulic boom cylinders for moving the boom arm assembly, and an implement assembly connected to the boom arm assembly. Typically, one or more hydraulic cylinders are used to manipulate the implement assembly. The implement assembly may be, for example, a bucket assembly, wherein the implement is a bucket and a pair of hydraulic bucket cylinders is used to move the bucket assembly. Other types of work vehicles that are similar to skid steer loaders include tractors, bulldozers and mini-excavators.
To operate the hydraulic boom cylinders and the hydraulic bucket cylinders, an operator in the cab manipulates either hand or foot manual controls. The skid steer loader, or similar work vehicle, includes an electronic control circuit system that includes an onboard computer, microprocessor, or controller. For the purposes of this disclosure a computer, microprocessor, or controller are considered to be equivalent and interchangeable elements. The onboard computer operates solenoids or digital coils of electroliydraulic valves that activate the hydraulic boom and bucket cylinders.
To properly operate the hydraulic boom cylinders and the hydraulic implement cylinders, each manual control is associated with a control and position sensor that generates input signals and sends them to the controller. The input signals generated by each sensor correspond proportionately to a displacement of the particular manual control from a neutral position. Generally, the neutral position is memorized and stored in the memory storage unit that is either integral with, or connected to, the controller. The controller receives the control and position sensor input signals, compares the information provided by these sensors to the memorized neutral position data, then generates output control signals used to control the operation of electrohydraulic valves, such as spool valves or cartridge valves, Thus, the controlled operation of the electrohydraulic valves activates the hydraulic cylinders of the boom arm assembly and the implement assembly to effect movement of the boom arm assembly and the implement carried by the boom arm assembly. In this way, an operator directs the desired movement on the boom arm assembly and the implement by manipulating manual controls in the cab of the work vehicle.
One such work vehicle is the skid steer loaded disclosed in U.S. Pat. No. 5,924,516 to Sagaser et al., which is incorporated herein by reference in its entirety. Sagaser et al. discloses an electronic control system for a skid steer loader (xe2x80x9cskidderxe2x80x9d) that includes a controller receiving inputs from an interface controller, position sensors associated with a hand grip and foot pedal manual controls, and a feedback signal from a linear actuator. The controller generates outputs to the linear actuator, which in turn activates a hydraulic spool valve that activates a hydraulic cylinder such as is connected to effect movement of a boom arm assembly or an implement carried by the boom arm assembly.
The hand grip and foot pedal manual controls are biased to a neutral position. The controller is programmed so that, upon power-up, the controller determines whether the manual controls are in a neutral position (or within some predetermined range of the neutral position) or not based on the data provided by position sensors associated with each manual control. If the manual controls are not in the neutral position, or not within some predetermined range of the neutral position, the controller sends a signal to the interface controller instructing the interface controller to inhibit certain operations of the loader until the manual controls are placed in the neutral position for some predetermined time period. In this manner, the loader is provided with a safety feature that prevents sudden and accidental operation of either the boom arm assembly and/or the implement assembly in case the operator starts up the loader with the manual controls significantly displaced from the neutral position.
However, the prior art work vehicles have certain drawbacks. First, the position information provided by the manual control and position sensors is susceptible to drift over time. Specifically, control and position sensors are partially sensitive to environmental changes such as variations in temperature. This dependence of each sensor on environmental factors is referred to as xe2x80x9csensor drift.xe2x80x9d Besides being partially temperature sensitive, the operational relationship between each control and position sensor and its associated manual control is partially sensitive to changes in the mechanical linkage between the manual controls and the sensors themselves. This dependence of the functioning of the sensor-manual control pair on the mechanical linkage between the sensor and the manual control is referred to, for the purposes of this disclosure, as xe2x80x9clinkage drift.xe2x80x9d The ever changing problem caused by the naturally occurring xe2x80x9csensor drift,xe2x80x9d i.e., sensor signal fluctuation secondary to temperature changes, and some degree of xe2x80x9clinkage drift,xe2x80x9d i.e., eventual changes over time in the mechanical linkage between the manual controls and the sensors themselves, is that the physical neutral position of the manual controls may not correspond precisely to the memorized neutral position. This drift in the physical neutral position from the memorized neutral position is referred to as xe2x80x9cneutral driftxe2x80x9d and is a function of, at least, sensor drift and linkage drift.
The prior art work vehicle has the disadvantage that the memorized neutral position stored in a memory storage device is fixed and there is no algorithm providing compensation for the neutral drift. The practical result of neutral drift is an eventual improper matching between the physical neutral position of the manual controls and the memorized neutral position stored in the memory storage device, which results in improper movement control of the boom arm assembly and/or the implement assembly when the physical neutral position is misperceived by the controller. Consequently, unexpected operation of the boom arm assembly and the implement assembly result as the manual controls are no longer precisely matched to movement in the boom arm assembly and implement assembly. In other words, the boom arm assembly and the implement can not be positioned as desired because the controller of the skid steer loader, or similar type of work vehicle, does not recognize when the manual controls are in the neutral position; therefore, the controller can not properly generate output control signals proportionate to the amount of displacement of the manual controls from the physical neutral position. Furthermore, when the controller can not properly recognize when the manual controls are in the neutral position, it becomes a more difficult task to get the controller to enable the operation of the boom arm assembly and the implement assembly instead of operating to inhibit operations of these assemblies.
From the previous discussion, it is clear that there is a need to correct for neutral drift. However, the particular amount of neutral drift between any one control and position sensor and its associated manual control is a physical limitation of the sensor and its mechanistic association with the manual control. In other words, the temperature dependence of any one particular control and position sensor is not readily predicable, and whatever play there is in the mechanical linkage between the sensor and its associated manual control is also unpredictable. Consequently, each sensor, paired to its manual control will form a system having unique neutral drift characteristics. Without extensive physical characterization of each individual sensor and characterization of the relationship with its associated manual control, it is impractical to confidently predict how much drift from the neutral position there will be with temperature changes and time related changes in the mechanical linkage between each sensor and its associated manual control. In other words, it is difficult or impractical to approach the problem of sensor neutral drift from the point of view of characterizing and correcting for each sensor and its mechanistic association with a manual control.
One object of the present invention is to overcome the disadvantages of the prior art electronic control systems for work vehicles and like machines.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that includes a feature for automatically correcting for neutral drift by using previously measured position sensor information collected at the moment of previous work vehicle start-ups and adding the most recently measured position sensor information collected at the moment of the present start-up to provide a xe2x80x9cmoving averagexe2x80x9d position that serves as the new neutral position of the manual controls for the work vehicle.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that permits the selection and enablement of either hand or foot manual controls to manipulate the boom arm assembly and the implement assembly, wherein neutral drift has been compensated for by the control system of the work vehicle.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that is practical and cost effective to manufacture.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that is both durable and reliable.
Although the electronic control system for work vehicles and like machines will be described for use in skid steer loaders and other similar work vehicles, another object of the present invention is to provide an electronic control system for machines having a boom arm assembly and an implement assembly connected to the boom assembly, wherein the machine can be a self-propelled vehicle or a stationary device.
In accordance with the above objects, thus is provided both method and apparatus embodiments in accordance with the present invention. In a first method embodiment in accordance with the present invention, a method of manual control neutral drift correction for a work vehicle is characterized by the steps of: (a) sensing a position of a first manual control using a first position sensor when an activation switch is activated, wherein the first position sensor generates a first input signal; (b) sending the first input signal to a controller; (c) retrieving a stored first manual control neutral position value from a memory unit; (d) calculating a first corrected manual control neutral position value using the controller, wherein the first corrected manual control neutral position value is calculated using the first input signal and the first manual control position value; and (e) utilizing the first corrected manual control neutral position value to generate a first control signal for operating a first electro-hydraulic valve, wherein the first control signal is generated by the controller to operate the first electro-hydraulic valve to effect movement of a first assembly.
In accordance with a second method embodiment of the present invention, the first method embodiment is further modified so that calculation of the first corrected manual control neutral position value is a weighted average calculated as a function of the first input signal and the first manual control position value. In accordance with a third method embodiment of the present invention, the second method embodiment is further modified so that the first corrected manual control neutral position value is the weighted average calculated using formula I:
NNA=[(PNA)*(nxe2x88x921)+NNU)]/nxe2x80x83xe2x80x83(I)
which is a moving average, where NNA is the first corrected manual control neutral position value, PNA is the first manual control neutral position value, NNU is the first input signal, and n=128.
In accordance with a fourth method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a right foot pedal manual control, the first position sensor is a right foot pedal implement position sensor, and the first assembly is an implement assembly, wherein the implement assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a fifth method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a left hand grip manual control, the first position sensor is a left hand stick boom arm position sensor, and the first assembly is a boom arm assembly, wherein the boom arm assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a sixth method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a left foot pedal manual control, the first position sensor is a left foot pedal boom arm position sensor, and the first assembly is a boom arm assembly, wherein the boom arm assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a seventh method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a right hand grip manual control, the first position sensor is a right hand stick implement position sensor, and the first assembly is an implement assembly, wherein the implement assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with an eighth method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a hand grip manual control, and the first position sensor is a hand rip position sensor.
In accordance with a ninth method embodiment of the present invention, the first method embodiment is further modified so that the first manual control is a foot pedal manual control, and the first position sensor is a foot pedal position sensor.
In accordance with a tenth method embodiment of the present invention, the eighth method embodiment is further modified so that the first assembly is an implement assembly.
In accordance with an eleventh method embodiment of the present invention, the ninth method embodiment is further modified so that the first assembly is an implement assembly.
In accordance with a twelfth method embodiment of the present invention, the eighth method embodiment is further modified so that the first assembly is a boom arm assembly.
In accordance with a thirteenth method embodiment of the present invention, the ninth method embodiment is further modified so that the first assembly is a boom arm assembly.
In accordance with a fourteenth method embodiment of the present invention, the first method embodiment is further modified so that activating the activation switch enables the first manual control and disables a second manual control.
In accordance with a fifteenth method embodiment of the present invention, the fourteenth method embodiment is further modified so that the first manual control is a right hand grip manual control, the second manual control is a right foot pedal manual control, the first position sensor is a right hand stick implement position sensor, and the first assembly is an implement assembly, wherein the implement assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a sixteenth method embodiment of the present invention, the fourteenth method embodiment is further modified so that the first manual control is a right foot pedal manual control, the second manual control is a right hand grip manual control, the first position sensor is a right foot pedal implement position sensor, and the first assembly is an implement assembly, wherein the implement assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a seventeenth method embodiment of the present invention, the fourteenth method embodiment is further modified so that the first manual control is a left hand grip manual control, the second manual control is a left foot pedal manual control, the first position sensor is a left hand stick boom position sensor, and the first assembly is a boom arm assembly, wherein the boom arm assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with an eighteenth method embodiment of the present invention, the fourteen method embodiment is further modified so that the first manual control is a left foot pedal manual control, the second manual control is a left hand grip manual control, the first position sensor is a left foot pedal boom position sensor, and the first assembly is a boom arm assembly, wherein the boom arm assembly moves when the first electro-hydraulic valve receives the first control signal.
In accordance with a nineteenth method embodiment of the present invention, the first method embodiment is further modified to include the steps of: (g) when the activation switch is activated, sensing a position of a second manual control using a second position sensor, sensing a position of a third manual control using a third position sensor, and sensing a position of a fourth manual control using a fourth position sensor, wherein the second position sensor generates a second input signal, the third position sensor generates a third input signal and the fourth position sensor generates a fourth input signal; (h) sending the second input signal, the third input signal and the fourth input signal to the controller; (i) retrieving a stored second manual control neutral position value, a stored third manual control neutral position value and a stored fourth manual control neutral position value from the memory unit; (j) calculating a second corrected manual control neutral position value using the controller, wherein the second corrected manual control neutral position value is calculated using the second input signal and the second manual control position value; (k) calculating a third corrected manual control neutral position value using the controller, wherein the third corrected manual control neutral position value is calculated using the third input signal and the third manual control position value; and (l) calculating a fourth corrected manual control neutral position value using the controller, wherein the fourth corrected manual control neutral position value is calculated using the fourth input signal and the fourth manual control position value.
In accordance with a twentieth method embodiment of the present invention, the nineteenth method embodiment is further modified to include the step of: (m) utilizing the second corrected manual control neutral position value to generate a second control signal for operating a second electro-hydraulic valve, wherein the second control signal is generated by the controller to operate the second electro-hydraulic valve to effect movement of a second assembly.
In accordance with a twenty-first method embodiment of the present invention, the twentieth method embodiment is further modified to include the step of: (n) storing the first corrected manual control neutral position value, the second corrected manual control neutral position value, the third corrected manual control neutral position value, and the fourth corrected manual control neutral position value in the memory unit.
In accordance with a twenty-second method embodiment of the present invention, the nineteenth method embodiment is further modified so that activating the activation switch enables the first manual control and the second manual control while disabling the third manual control and the fourth manual control.
In accordance with a twenty-third method embodiment of the present invention, the first method embodiment is further modified to include the step of: (f) storing the first corrected manual control neutral position value in the memory unit.
In a first apparatus embodiment in accordance with the present invention, a work vehicle is characterized by: (a) a frame; (b) a boom arm assembly connected at one end to the frame; (c) an implement assembly pivotally connected to another end of the boom arm assembly, wherein the implement assembly includes an implement; (d) a first hydraulic implement cylinder connected to the implement assembly and positioned to pivotally rotate the implement relative to the boom arm assembly when a piston of the first hydraulic implement cylinder is extended or retracted, wherein the first hydraulic implement cylinder is connected to a first electrohydraulic valve that activates extension and retraction of the piston of the first implement cylinder; (e) a second hydraulic boom cylinder connected to the boom arm assembly and positioned to move the boom arm assembly between a first retracted position and a second extended position when a piston of the second boom cylinder is retracted and extended, respectively, wherein the second hydraulic boom cylinder is connected to a second electrohydraulic valve that activates extension and retraction of the piston of the second hydraulic cylinder; (f) a first position sensor disposed to sense a position of a first manual control and generate a first input signal; (g) a second position sensor disposed to sense a position of a second manual control and generate a second input signal; (h) a controller connected to receive the first input signal from the first position sensor and the second input signal from the second position sensor, and connected to send a first control signal to the first electrohydraulic valve and a second control signal to the second electrohydraulic valve; and (i) an activation switch connected to send an activation signal to the controller, wherein when the activation signal is sent to the controller, the controller retrieves a first manual control neutral position value and a second manual control neutral position value from a memory storage device connected to provide stored data to the controller and the controller calculates a first corrected manual control neutral position value and a second corrected manual control neutral position value using the first input signal, the second input signal, the first manual control neutral position value and the second manual control neutral position value, wherein the controller generates the first control signal using the first corrected manual control neutral position value and generates the second control signal using the second corrected manual control neutral position value.
In accordance with a second apparatus embodiment of the present invention, the first apparatus embodiment is further modified to include a third position sensor disposed to sense a position of a third manual control and generate a third input signal; and a fourth position sensor disposed to sense a position of a fourth manual control and generate a fourth input signal, wherein the controller is connected to receive the third input from the third position sensor and to receive the fourth input from the fourth position sensor, wherein when the activation signal is sent to the controller, the controller retrieves a third manual control neutral position value and a fourth manual control neutral position value from the memory storage device connected to provide stored data to the controller and the controller calculates a third corrected manual control neutral position value and a fourth corrected manual control neutral position value using the third input signal, the fourth input signal, the third manual control neutral position value and the fourth manual control neutral position value.
In accordance with a third apparatus embodiment of the present invention, the second apparatus embodiment is further modified so that the first manual control and the second manual control are manual hand grip controls and the third manual control and the fourth manual controls are manual foot pedal controls, wherein the controller enables the first manual control and the second manual control and disables the third manual control and the fourth manual control in response to receiving the activation signal from the activation switch.
In accordance with a fourth apparatus embodiment of the present invention, the second apparatus embodiment is further modified so that the first manual control and the second manual control are manual foot pedal controls and the third manual control and the fourth manual controls are manual hand grip controls, wherein the controller enables the first manual control and the second manual control and disables the third manual control and the fourth manual control in response to receiving the activation signal from the activation switch.
In accordance with a fifth apparatus embodiment of the present invention, the second apparatus embodiment is further modified so that the memory storage device is integrally connected to the controller and forms a portion of the controller.
In accordance with a sixth apparatus embodiment of the present invention, the second apparatus embodiment is further modified so that the memory storage device is an external non-volatile memory unit connected to the controller.
Further objects, features, and advantages of the present invention will become apparent from the Detailed Description of Preferred Embodiments, which follows, when considered together with the attached drawings.